The glass-molding process for planar-integrated micro-optical component

This paper presents a precision glass-molding process to fabricate planar-integrated micro-optical components (PIMOC) applied to a micro projection display system, optical interconnection system and optical storage system. The PIMOC was designed based on wave propagation theory, and fabricated using a glass molding process. Experimental results are discussed in this article. The experiment showed that the PIMOC fabricated in a vacuum environment meets the design value with precision glass-molding technology (PGMT) at a molding force of 2.75 kN, a molding temperature of 750 °C and a cooling rate of 49 °C/min.     

XRD study on the effect of the deposition condition on pulsed laser deposition of ZnO films

Using a pulsed laser deposition (PLD) process on a ZnO target in an oxygen atmosphere, thin films of this material have been deposited on Si(111) substrates. An Nd: YAG pulsed laser with a wavelength of 1064 nm was used as the laser source. The influences of the deposition temperature, laser energy, annealing temperature and focus lens position on the crystallinity of ZnO films were analyzed by X-ray diffraction. The results show that the ZnO thin films obtained at the deposition temperature of 400°C and the laser energy of 250 mJ have the best crystalline quality in our experimental conditions. The ZnO thin films fabricated at substrate temperature 400°C were annealed at the temperatures from 400°C to 800°C in an atmosphere of N₂. The results show that crystalline quality has been improved by annealing, the optimum temperature being 600°C. The position of the focusing lens has a strong influence on pulsed laser deposition of the ZnO thin films and the optimum position is 59.5 cm from the target surface for optics with a focal length of 70 cm.      

Skin Thickness and β-Crystals Development in Injection-Molded iPP Along the Flow Direction

In this study, iPP was injection molded at 180°C, 200°C, and 220°C. According to polarization optical microscopy (POM) results, for a given part, the skin thickness steadily decreases along the flow direction. However, at the same distance from the gate, the skin thickness of the parts molded at lower melt temperature is larger than that molded at higher melt temperature. It is found that flow time (here, the time taken for melt to pass the specific position along the flow direction) and melt temperature are two significant factors leading to this phenomenon, while the gate size is another one.

The DSC and WAXD results show that the relative fraction of β-form crystals, for a specific part, decreases along the flow direction, which is mainly determined by flow time. However, for the parts molded at different molding temperatures, the fraction of the β-form crystals is mainly determined by the molding temperature, though this influence is very complex.     

A wide-FoV athermalized infrared imaging system with a two-element lens

For infrared imaging systems to achieve wide field of view (FoV), wide operating temperature and low weight, this work designs a wide-FoV athermalized infrared imaging system (AIIS) with a two-element lens. Its principle, design, manufacture, measurement and performance validation are successively discussed. The two-element lens contains four surfaces, where three aspheric surfaces are introduced to reduce optical off-axis aberrations and a cubic surface is introduced to achieve athermalization. The key coding mask containing an aspheric surface and a cubic surface is manufactured by nano-metric machining of ion implanted material (NiIM). Experimental results validate that our wide-FoV wavefront coding AIIS has a full FoV of 26.10° and an operating temperature over –20 °C to +70 °C.     

Direct Resinification of Two (1→3)-β-D-Glucans,Curdlan and Paramylon,via Hot-Press Compression Molding

Abstract

Hot-press compression molding was attempted to resinify two renewable source-derived linear (1→3)-β-D-glucan polymers, i.e., paramylon or curdlan via the generation of reactive aldehyde groups that tend to crosslink with hydroxyl groups of the glucans. As for the paramylon, the optimal molding temperature was found to be around 220?°C, keeping the pressure at 20?MPa for 3?min, due to its highly crystalline structure. On the other hand, the curdlan resin was producible in the temperature range of 180–240?°C at the same pressure and pressing time. Dynamic mechanical analysis revealed a large temperature dependence of the loss modulus, E’’, for the paramylon-based polymer resin whereas the semi-crystalline curdlan resin was stable in terms of both the storage and loss moduli, E’ and E’’, up to 160?°C. The vaporization of the water formed during the molding, due to the thermal decomposition, and the adsorption of moisture due to the hydrophilic property of the paramylon affected the thermal stability. The curdlan resin exhibited flexural strength and modulus extremely superior to those of regenerated and esterified curdlan films, and even a little superior to those of polyamide-12. The strain at break was comparable to the yield strain of an epoxy resin. On the other hand, the paramylon-based polymer resin was producible, but the resinification property and thermal stability of the paramylon resin was inferior to the curdlan resin due to the former’s highly crystalline structure.     

Adhesive As-S-Se-I immersion lenses for enhancing radiation characteristics of mid-IR LEDs operating in wide temperature range

The influence of As-S-Se-I chalcogenide glass lenses on the integral and spectral power and pattern of LED radiation has been shown. Simulation of the influence of the refractive index on the integral power for two lens shapes has been performed. The wettability and adhesion force of As-S-Se-I melt has been determined for several electronic engineering materials. Mechanical stresses between chalcogenide glass and adjacent diode body materials have been calculated for −100 to 53 °C temperature range. Stability of the immersion lenses against cracking has been experimentally investigated for −150 to 53 °C temperature range.     

SITE-RESOLVED WIDE-ANGLE X-RAY STUDIES ON STRUCTURAL PP FOAMS INJECTION-MOLDED BY THE LOW-PRESSURE PROCESS

Structural foam specimens, consisting of three co-axial cylinders of different diameter and length, were injection-molded from isotactic polypropylene, mixed with 0.5 wt% azodicarbonamide as blowing agent, by the classical low-pressure process in a mold cavity (temperature 20°C) pre-pressurized with nitrogen, at melt temperatures of 200, 220, and 240°C, applying different sprue systems and injection directions. Cross-sections were cut from the middle of each cylinder in longitudinal orientation and investigated by site-resolved wide-angle x-ray scattering, making use of the so-called “parallel transmission” geometry. The measurements yielded detailed information about the orientation, dimensions, and interplanar spacings of α-PP crystallites, the distribution of β-PP, and the crystallinity in the cross-sections of the moldings and led to the establishment of general relations between the molding conditions and the microstructure of the moldings in dependence on the configuration of the specimens.     

High stability of electro-optically Q-switched Ce:Nd:YAG laser by using the optimized concavo-convex cavity

In order to solve the hard problem of laser instability, an electro-optically Q-switched Ce:Nd:YAG laser by using the optimized concavo-convex cavity is demonstrated. The laser with the optimized cavity is insensitive to the thermal lens of laser crystal and has excellent stability of average output pulse energy and threshold voltage under different environment temperature of −45, 25, and 55°C.     

Differential thermal analysis at high pressures—VII: Phase behaviour of solid methanol up to 3kbar

The phase behaviour of solid methanol was investigated from -196°C to the melting temperature and up to 3 kbar, using a low-temperature high-pressure dta apparatus. The melting temperature rises from -98°C at 1 atm to -64°C at 2775 bar. Solid methanol exhibits a transition at atmospheric pressure at approximately -115°C; the transition has a strong tendency to superheat and to occur at -110°C. The transition temperature rises from approximately -115°C at 1 atm to -81°C at 2725 bar. Small impurities of water induce a “second transition” at -117.3°C that must be attributed to the water-methanol eutectic. Volume changes accompanying the phase transition have been calculated using the Clausius Clapeyron equation.     

The iron mineral changes occurring in lignite coal during gasification

Representative lignite and gasified material samples were retrieved form a cooled down gasifier. The samples were taken at various heights in the gasifier that operated on lignite, under stable conditions. The proximate analyses, ash composition and temperature in the gasifier were determined according to standard procedures. The main minerals found in the present investigation were bassanite, illite, quartz, kaolinite, calcite and the only iron bearing mineral was found to be pyrite. The trend in the estimated particle surface temperature profile shows an increase in the drying, pyrolysis, gasification and combustion zones from about 300 °C to just over 900 °C. About 1/3 down the gasifier, an average particle temperature of about 400 °C and particle surface temperature of about 600 °C was measured where pyrite conversion started. About 2/3 down the gasifier, where an average temperature of about 700 °C and particle surface temperature of about 900 °C was measured, all the pyrite was converted and in the bottom part of the gasifier, oxidation of the iron started to play a role and hematite and an iron containing glass formed at an average temperature of > 800 °C and surface temperature of 900 °C.     

Thermal diffusivity study of cheese fats by thermal lens detection

In this paper we used thermal lens spectrometry to determine the thermal diffusivity of cheese fats. We have used equal concentrations of cheese fats from oaxaca, chihuahua, gouda, manchego and mozzarella cheeses at 42°C temperature. The two lasers mismatched mode experimental configuration was used with a He-Ne laser, as a probe beam and an Ar⁺ laser as the excitation one. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression to the experimental data in order to obtain the thermal diffusivity of the cheese fat samples. This measured thermal property may contribute to a better understanding of the cheese fats quality, which is very important in food industry.     

Hot electron studies of lattice damage created in silicon by implantation of 2.8 MeV protons

Abstract

In this paper we report the results of a study of the annealing properties of the ionized defect density associated with the damage created in the silicon lattice by implantation of 2.8 MeV protons at room temperature. In particular, the annealing of damage created by implanting to a level of 4.43 × 10¹² protons/cm² is reported. The resulting isochronal annealing curve covered the temperature range from 70°C to 460°C. Two major annealing stages are discussed, one a broad stage between 70°C to 200°C and the other an abrupt annealing stage between 440°C to 460°C. Between the temperature range 200°C to 440°C the number of ionized defects remained relatively constant. Above 460°C no detectable effects of the proton implantation remained.     

Biaxially Self-Reinforced High-Density Polyethylene Prepared by Vibration-Assisted Injection Molding. I. Processing Conditions and Physical Properties

A pulse pressure was imposed on the melt in the injection molding cavity during the injection and holding pressure stages, called vibration-assisted injection molding (VAIM) technology. With the VAIM technology, biaxially self-reinforced high-density polyethylene (HDPE) samples were prepared and the physical properties affected by the vibration processing conditions were studied. The tensile properties can be improved in both the machine direction (MD) and the transverse direction (TD) by changing the vibration frequency and vibration pressure amplitude, respectively. The elongation at break increased with increasing the vibration frequency for the VAIM sample processed at constant low vibration pressure amplitude; the yield strength increased with increasing the vibration pressure amplitude for the VAIM sample prepared at constant low vibration frequency. The softening point temperature for the VAIM sample increased by 8°C compared with a conventional injection-molded (CIM) sample.     

Behavior of thermocouples under high pressure in a multi-anvil apparatus

We have conducted experiments to study the behavior of W5%Re–W26%Re (type C) and Pt10%Rh–Pt (type S) thermocouples under high pressure in a multi-anvil apparatus. The electromotive force (emf) between four different or three identical thermocouple wires was measured up to 15?GPa and 2100?°C. Mechanical and chemical stability of the thermocouples was examined during and after the experiments. Due to the effect of pressure on the emf/temperature relation, the temperature reading of the type C minus that of the type S thermocouple rises to +5?°C then falls to ?15?°C between room temperature and 1500?°C at 5?GPa, and to +25?°C and then ?35?°C between room temperature and 1800?°C at 15?GPa. In addition, we observed variations in the emf/temperature relation caused by uncertainties in the position and geometry of hot junctions in a steep temperature gradient, and by variable distribution of pressure gradient and non-hydrostatic stress on the thermocouple wires. These errors are estimated at 1.6% for the type S thermocouple up to 1700?°C, and 0.8% for the type C thermocouple up to 2100?°C. Self-diffusion and chemical contamination of the thermocouples by high-purity insulating ceramics appear negligible for the type S thermocouple at 1700?°C for one hour, and for the type C thermocouple at 2100?°C for half an hour. In contrast, large-scale displacement of the hot junction due to dislocation of the type C thermocouple wires and plastic deformation of the type S thermocouple wires may lead to large errors in temperature measurement (±200?°C).     

Excellent stability of laser passively Q-switched with a retroreflecting corner cube prism

A miniature Cr⁴⁺:YAG Q-switched, repetitive operation, conductive cooling Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism which is insensitive to misalignment in any direction makes it useful for the laser to adapt to the violent change of ambient temperature and also makes the laser cavity insensitive to the variation of thermal lens of the crystal. The laser has excellent stability of the average output pulse energy and the threshold voltage under different ambient temperature of −40, 25, and 55°C.     

Crystallization behaviour of PZT in multilayer heterostructures

Microstructural and electrical properties of PZT (lead zirconate titanate) thin films prepared by sol-gel techniques at annealing temperatures in the range from 550°C to 900°C are studied. Perovskite (Pe) grain nucleation in PZT film starts but not completes at 550°C. Along with formation of round Pe (111) grains on the Pt (111) interface, the film contains small Pe and pyrochlore (Py) grains. Films annealed at the temperatures higher than 600°C demonstrate column structure of Pe grains, the amount of Py inclusions reduces with the annealing temperature and practically disappears at 700°C. An increase of annealing temperature leads to enhancement of (100) Pe orientation as a result of Ti diffusion on the Pt surface. Polarization decreases with the annealing temperature (maximum at 600°C), whereas permittivity increases up to the annealing temperature of 750°C.     

The effect of annealing temperature on the morphology and piezoelectric characteristics of BaTiO3 nanofibers and domain switching under different temperatures

Effects of annealing temperature (600–750 °C) on crystalline structure, the morphology and piezoresponse hysteresis loops of BaTiO₃ nanofibers prepared by electrospinning are characterized by X-ray diffraction, scanning electronic microscopy, transmission electron microscope and piezoresponse force microscope. When the annealing temperature is 700 °C, the nanofibers become smoother and have a diameter of 100–300 nm. Meanwhile the typical butterfly-shaped amplitude loop and 180°phase change represents the best ferroelectric and piezoelectric properties at 700 °C. So the 700 °C was found to be optimum for good piezoelectric characteristics at annealing temperature of 600 °C–750 °C. In order to give more clear evolution of domain states at different external fields, the three dimensional topographic and phase images of the nanofiber at different temperatures are observed by piezoresponse force microscope. The 90° domain switching is observed during heating from room temperature to 125 °C and the domain switching tends to be stable when the temperature exceeds a critical value. The thermal stress due to the high temperatures is responsible for switching mechanism from the perspective of equilibrium state free energy. This work suggests that the temperature variation should be considered while designing the ferroelectric devices based on one dimensional material.     

Study on the temperature dependence of BGO light yield

The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of-30–30℃. The temperature coefficient of the BGO and R5610 A as a whole was tested to be-1.82%/℃. And the temperature coefficient of the gain of the R5610 A is-0.44%/℃ which was tested in the same situation using a blue LED. Thus the temperature coefficient of BGO's light yield can be evaluated as-1.38%/℃.     

Luminescence lifetimes in quartz: dependence on annealing temperature prior to beta irradiation

It is well known that the thermal history of a quartz sample influences the optically stimulated luminescence sensitivity of the quartz. It is found that the optically stimulated luminescence lifetime, determined from time resolved spectra obtained with pulsed stimulation, also depends on past thermal treatment. For samples at 20°C during stimulation, the lifetime depends on beta dose and on duration of preheating at 220°C prior to stimulation for quartz annealed at 600°C and above, but is independent of these factors for quartz annealed at 500°C and below. For stimulation at higher temperatures, the lifetime becomes shorter if the sample is held at temperatures above 125°C during stimulation, in a manner consistent with thermal quenching. A single exponential decay is all that is required to fit the time resolved spectra for un-annealed quartz regardless of the temperature during stimulation (20–175°C), or to fit the time resolved spectra from all samples held at 20°C during stimulation, regardless of annealing temperature (20–1000°C). An additional shorter lifetime is found for some combinations of annealing temperature and temperature during stimulation. The results are discussed in terms of a model previously used to explain thermal sensitisation. The luminescence lifetime data are best explained by the presence of two principal luminescence centres, their relative importance depending on the annealing temperature, with a third centre involved for limited combinations of annealing temperature and temperature during stimulation.     

Study of the structural phase transformation,and optical behavior of the as synthesized ZnO–SnO2–TiO2 nanocomposite

Bulk nanocomposites ZnO–SnO₂–TiO₂ were synthesized by solid-state reaction method. The X-ray diffraction patterns and Raman spectra of bulk nanocomposite as a function of sintering temperature (700 °C–1300 °C) indicate that the structural phases of SnO₂ and TiO₂ depend on the sintering temperature while the ZnO retains its hexagonal wurtzite phase at all sintering temperatures and SnO₂ started to transform into SnO at 900 °C and completely converted into SnO at 1100 °C, whereas the titanium dioxide (TiO₂) exhibits its most stable phase such as rutile at low sintering temperature (≤900°C) and it transforms partially into brookite phase at high sintering temperature (≥ 900 °C). The optical band gap of nanocomposite ZnO–SnO₂–TiO₂ sintered at 700 °C, 900 °C, 1100 °C and 1300 °C for 16 hours is calculated using the transformed diffuse reflectance ultra violet visible near infra red (UV–VisNIR) spectra and has been found to be 3.28, 3.29, 3.31 and 3.32 eV, respectively.